A Lookahead Read Cache: Improving Read Performance of Deduplication Storage for Backup Applications

Abstract—Data deduplication (for short, dedupe) is a special data compression technique and has been widely adopted especially in backup storage systems with the primary aims of backup time saving as well as storage saving. Thus, most of the traditional dedupe research has focused more on the write performance improvement during the dedupe process while very little effort has been made at read performance. However, the read performance in dedupe backup storage is also a crucial issue when it comes to the storage recovery from a system crash. In this paper, we newly design a read cache in dedupe storage for a backup application to improve read performance by taking advantage of its special characteristic: the read sequence is the same as the write sequence. Thus, for better cache utilization, we can evict the data containers with smallest future references from the cache by looking ahead their future references in a moving window. Moreover, To achieve better read cache performance, our design maintains a small log buffer to judiciously maintain future access data chunks. Our experiments with real world workloads demonstrates that our proposed read cache scheme makes a big contribution to read performance improvement.